'use strict';

const assert = require('assert').strict;

// Convert IP string to number
//   ip <string> - IP address
// Returns: <number>
const ipToInt = ip => ip.split('.')
  .reduce((res, item) => (res << 8) + +item, 0);

// Tests

{
  const n = ipToInt('127.0.0.1');
  // ['127', '0', '0', '1']
  // 0 << 8 = 0
  // 0 + 127 = 127
  // 0 + 127 << 8 = 32512
  // 32512 << 8 = 8323072
  // 8323072 << 8 = 2130706432
  // 2130706432 + 1 = 2130706433
  // 1111111000000000000000000000001
  assert.strictEqual(n, 2130706433, 'Localhost IP address');
}

{
  const n = ipToInt('10.0.0.1');
  assert.strictEqual(n, 167772161, 'Single class A network');
}

{
  const n = ipToInt('192.168.1.10');
  assert.strictEqual(n, -1062731510, 'Negative number');
}

{
  const n = ipToInt('0.0.0.0');
  assert.strictEqual(n, 0, 'Four zeros');
}

{
  const n = ipToInt('wrong-string');
  assert.strictEqual(n, Number.NaN, 'Wrong string');
}

{
  const n = ipToInt('');
  assert.strictEqual(n, 0, 'Empty string');
}

{
  const n = ipToInt('8.8.8.8');
  assert.strictEqual(n, 0x08080808, 'Four eights');
}
